Methods for processing nanostructured ferritic alloys, and articles produced thereby

ABSTRACT

A method of forming an article including a nanostructured ferritic alloy is provided. The method provides steps for substantially inhibiting grain growth of a workpiece that includes nanostructured ferritic alloy, during heating and deforming at high temperatures and at high strain rates. Advantageously, the article is formed via conventional high strain rate techniques and thus, cost savings are provided. Articles are also provided which are formed by the method, and the articles so produced exhibit good mechanical properties at high operating temperatures, and thus are utilized as turbomachinery components, and in particular, component of a heavy duty gas turbine or steam turbine. A turbomachinery component comprising an NFA is provided.

BACKGROUND

The present disclosure relates to nanostructured ferritic alloys (NFAs),and more particularly, methods for processing the same utilizing hightemperature processing methods. The disclosure also relates to anarticle comprising a nanostructured ferritic alloy (NFA) that is formedby using such a method.

Gas turbines operate in extreme environments, exposing the turbinecomponents, especially those in the turbine hot section, to highoperating temperatures and stresses. In order for the turbine componentsto endure these conditions, they are necessarily manufactured from amaterial capable of withstanding these severe conditions. In otherwords, a material used for the turbine components limits the temperaturerange that can be used without inducing a significant degradation in themechanical properties of the material.

Superalloys have been used in these demanding applications because theymaintain their strength at up to 90% of their melting temperature andhave excellent environmental resistance. Nickel-based superalloys, inparticular, have been used extensively throughout the gas turbineengines, e.g., in turbine blade, nozzle, wheel, spacer, disk, spool,blisk, and shroud applications. In some lower temperature and stressapplications, steels may be used for turbine components. However, use ofconventional steels is often limited in high temperature and high stressapplications because they fail to meet necessary mechanical propertyrequirements and/or design requirements.

Nanostructured ferritic alloys (NFAs) are an emerging class ofiron-based alloys that exhibit exceptional high temperature properties.These alloys are typically derived from nanometer-sized oxideparticulates or clusters that precipitate during hot consolidationfollowing a mechanical alloying step. These oxide particulates orclusters are present at high temperatures, providing a strong and stablemicrostructure during service.

The NFAs are a powder metallurgy alloy that is typically consolidatedthrough hot iso static pressing (HIP), and then hot-worked tomanufacture a desired article. However, processing an as-HIP NFA at ahigh temperature, for example higher than about 1900 degrees Fahrenheit(° F.), typically leads to a change in its final microstructure and thusresults in the degradation of its mechanical properties. This change inmicrostructure at the high temperatures limits (1) the use of these NFAmaterials at desired temperatures and stresses, for example in a heavyduty gas turbine, and (2) the use of the high strain rate processingtechniques that may be economically beneficial for manufacturing anarticle.

In order for any material to be optimally useful in the desiredapplication, for example, components for heavy duty turbomachinery, thematerial should desirably be capable of being manufactured into thedesired article without sacrificing its mechanical properties. It mayadditionally be desirable to process the material at high temperaturesand high strain rates.

BRIEF DESCRIPTION

In some embodiments, a method for forming an article comprising ananostructured ferritic alloy is provided. The method includesintroducing a quantity of strain into a workpiece at a first temperatureto form a strained workpiece, heating the strained workpiece to a secondtemperature, and deforming the strained workpiece at the secondtemperature. The workpiece includes a nanostructured ferritic alloy. Thefirst temperature is below about 1900 degrees Fahrenheit and the secondtemperature is at least about 1900 degrees Fahrenheit. The quantity ofstrain introduced into the workpiece at the first temperature iseffective to substantially inhibit grain growth in the strainedworkpiece during the subsequent heating and the deforming at the secondtemperature.

In some embodiments, there is provided an article comprising ananostructured ferritic alloy, which may be formed by the method. Thearticle may be a turbomachinery component.

In some embodiments, a method of forming a turbomachinery componentcomprising a nanostructured ferritic alloy is provided. The methodincludes introducing a quantity of strain into a workpiece at a firsttemperature to form a strained workpiece, heating the strained workpieceto a second temperature, and forging the strained workpiece at thesecond temperature at a strain rate of at least about 1 inch/inch/sec.The workpiece includes a nanostructured ferritic alloy. The firsttemperature is below 1900 degrees Fahrenheit and the second temperatureis higher than 1900 degrees Fahrenheit. The quantity of strainintroduced into the workpiece at the first temperature is effective tosubstantially inhibit grain growth in the strained workpiece during thesubsequent heating and the forging at the second temperature.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawing, wherein

FIG. 1A shows scanning electron microscope (SEM) micrograph of an“as-consolidated” NFA workpiece.

FIG. 1B shows SEM micrograph of the NFA workpiece after heating theworkpiece at 2000 Fahrenheit for 24 hours after the consolidation.

FIG. 2A shows SEM micrograph of a NFA workpiece that is extruded at 1700degrees Fahrenheit, in accordance with some embodiments of theinvention.

FIG. 2B shows SEM micrograph after heating the extruded NFA workpiece at2000 degrees Fahrenheit, in accordance with some embodiments of theinvention.

FIG. 3 shows stress-strain curves for NFA workpieces that are processedwith high strain rates at 1900 degrees Fahrenheit and 2100 degreesFahrenheit, in accordance with some embodiments of the invention.

DETAILED DESCRIPTION

Unless defined otherwise, technical and scientific terms used hereinhave the same meaning as is commonly understood by one of skill in theart to which this invention belongs. The terms “comprising,”“including,” and “having” are intended to be inclusive, and mean thatthere may be additional elements other than the listed elements. Theterms “first”, “second”, and the like, as used herein do not denote anyorder, quantity, or importance, but rather are used to distinguish oneelement from another. Also, the terms “a” and “an” do not denote alimitation of quantity, but rather denote the presence of at least oneof the referenced item, and the terms “front”, “back”, “bottom”, and/or“top”, unless otherwise noted, are merely used for convenience ofdescription, and are not limited to any one position or spatialorientation.

If ranges are disclosed, the endpoints of all ranges directed to thesame component or property are inclusive and independently combinable(e.g., ranges of “up to about 25 wt. %, or, more specifically, about 5wt. % to about 20 wt. %,” is inclusive of the endpoints and allintermediate values of the ranges of “about 5 wt. % to about 25 wt. %,”etc.). The modifier “about” used in connection with a quantity isinclusive of the stated value and has the meaning dictated by thecontext (e.g., includes the degree of error associated with measurementof the particular quantity).

As discussed in detail below, some embodiments of the invention includea method for processing a nanostructured ferritic alloy (NFA) thatallows the alloy (NFA) to be processed at a high temperature, a highstrain rate, or both at high temperature and high strain rate whilemaintaining a desired microstructure. Some embodiments provide articles(also referred to as “formed articles”) manufactured by the presentmethod. In one embodiment, the formed article is made of ananostructured ferritic alloy (NFA), wherein the article is formed at ahigh temperature, a high strain rate, or both. The formed article may beany article desirably comprising the NFA and the properties conferredthereto by the NFA.

One illustrative class of articles that may find particular benefit fromapplication of the principles described herein includes turbomachinerycomponents, and in particular, those that experience high operatingtemperatures (for example, greater than 850° F.) and/or high stressesduring use. In some embodiments, the formed article may advantageouslycomprise a component of a gas turbine or a steam turbine. Some exemplaryarticles are bolts, studs, blades, wheels, and spacers.

The nanostructured ferritic alloys (NFAs) are a class of alloys thatcomprise a stainless steel matrix that is dispersion strengthened by avery high density, for example, at least about 10¹⁸ m⁻³ of nanometer(nm)-scale, i.e., from about 1 nanometer to about 100 nanometers, ofnanofeatures comprising titanium oxide (Ti—O) and at least one othermetal element from the oxide used to prepare the NFA or the alloymatrix. For example, yttrium oxide, aluminum oxide, zirconium oxide,hafnium oxide may be used to prepare the NFAs, in which case, thenanofeatures may comprise yttrium (Y), aluminum (Al), zirconium (Zr),hafnium (Hf) or combinations of these. Transition metals, such as iron(Fe), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn),silicon (Si), niobium (Nb), aluminum (Al), nickel (Ni), or tantalum (Ta)from the alloy matrix can also participate in the creation of thenanofeatures. In some embodiments, an average size of nanofeaturesranges from about 1 nanometer to about 50 nanometers. In certaininstances, the average size ranges from about 1 nanometer to about 10nanometers. The density of nanofeatures, in some instances, is at leastabout 10²⁰ m⁻³, and in some certain instances, at least about 10²² m⁻³.

In contrast, conventional oxide dispersion strengthened (ODS) alloysgenerally contain refined, but larger, oxide phases, and the oxideadditive is stable throughout the powder metallurgy process, i.e., ifyttrium oxide were added to the matrix alloy, ytrrium oxide would bepresent after the alloying step and there would be no significantformation of the nanofeatures (NFs) described above. In an NFA, at leastthe majority, and in some cases substantially all, of the added oxide isdissolved into the alloy matrix during powder attrition and participatesin the formation of the aforementioned nanofeatures when the powder israised to a temperature during the compaction process, for example hotisostatic pressing (HIP). As described above, the new oxide in the NFAmay comprise one or more transition metals present in the base alloy aswell as the metallic element(s) of the initial oxide addition.

In one embodiment, the nanostructured ferritic alloy (NFA) comprises aferritic stainless steel. In certain other embodiments, a martensitic,duplex, austenitic stainless steel or precipitation hardened steel arealso potential matrix alloys. The nature of the steel matrix phase mayaffect to some degree the environmental resistance and the materialductility of the resultant NFA.

In one embodiment, the NFA includes chromium. Chromium can be importantfor ensuring corrosion resistance, and may thus be included in the NFAin amounts of at least about 5 weight percent, and in some embodiments,at least about 9 weight percent. Amounts of up to about 30 weightpercent, and in some instances up to about 20 weight percent can beincluded. Advantageously, both chromium and iron, the basis of the NFA,are readily available and relatively low in cost, in particular ascompared to the nickel-based superalloys which the NFAs may replace insome applications.

In some embodiments, the NFA includes molybdenum. An amount of up toabout 30 weight percent, and in some instances, up to about 20 weightpercent can be included. In some instances, the amount of molybdenumranges from about 3 weight percent to about 10 weight percent. In someother instances, the amount of molybdenum ranges from about 1 weightpercent to about 5 weight percent.

The NFA may further include titanium. Titanium may participate in theformation of the precipitated oxide, and so, amounts of titanium of fromabout 0.1 weight percent to about 2 weight percent, and in someinstances, from about 0.1 weight percent to about 1 weight percent, andin certain instances, from about 0.1 weight percent to about 0.5 weightpercent, are desirably included in the NFA.

The composition of the nanofeature(s) will depend, in part, upon theoxide utilized to prepare the NFA and/or the alloy matrix. Typically,the nanofeatures comprise titanium, oxygen and one or more additionalelement such as Y, Zr, Hf, Fe, Cr, Mo, W, Mn, Si, Nb, Al, Ni, Ta, or anycombination of aforementioned. Generally, an NFA as described hereincomprises at least about 0.1% oxygen by weight. The amount of oxygenpresent in the alloy determines in part the resultant type andconcentration of nanofeatures present in the alloy. In some embodiments,the oxygen content is in a range from about 0.1% to about 0.5%, and inparticular embodiments, the range is from about 0.1% to about 0.3%,where all percentages are by total weight of the alloy.

One illustrative NFA suitable for use in the formation of the articlecomprises from about 5 weight percent to about 30 weight percentchromium, from about 0.1 weight percent to about 2 weight percenttitanium, from about 0 weight percent to about 10 weight percentmolybdenum, from about 0 weight percent to about 5 weight percenttungsten, from about 0 weight percent to about 5 weight percentmanganese, from about 0 weight percent to about 5 weight percentsilicon, from about 0 weight percent to about 2 weight percent niobium,from about 0 weight percent to about 2 weight percent aluminum, fromabout 0 weight percent to about 8 weight percent nickel, from about 0weight percent to about 2 weight percent tantalum, from about 0 weightpercent to about 0.5 weight percent carbon, and from about 0 weightpercent to about 0.5 weight percent nitrogen, with the balance beingiron and incidental impurities; and a number density of at least about10¹⁸ m⁻³ nanofeatures comprising titanium, oxygen, and at least oneelement derived from the oxide added during the preparation of the NFAor from the alloy matrix.

In other embodiments, the NFA comprises from about 9 weight percent toabout 20 weight percent chromium, from about 0.1 weight percent to about1 weight percent titanium, from about 0 weight percent to about 10weight percent molybdenum, from about 0 weight percent to about 4 weightpercent tungsten, from about 0 weight percent to about 2.5 weightpercent manganese, from about 0 weight percent to about 2.5 weightpercent silicon, from about 0 weight percent to about 1 weight percentniobium, from about 0 weight percent to about 1 weight percent aluminum,from about 0 weight percent to about 4 weight percent nickel, from about0 weight percent to about 1 weight percent tantalum, from about 0 weightpercent to about 0.2 weight percent carbon, and from about 0 weightpercent to about 0.2 weight percent nitrogen, with the balance beingiron and incidental impurities; and a number density of at least about10²⁰ m⁻³ nanofeatures comprising titanium, oxygen and at least oneelement derived from the oxide added during the preparation of the NFAor from the alloy matrix.

In yet other embodiments, the NFA comprises from about 9 weight percentto about 14 weight percent chromium, from about 0.1 weight percent toabout 0.5 weight percent titanium, from about 0 weight percent to about10 weight percent molybdenum, from about 0 weight percent to about 3weight percent tungsten, from about 0 weight percent to about 1 weightpercent manganese, from about 0 weight percent to about 1 weight percentsilicon, from about 0 weight percent to about 0.5 weight percentniobium, from about 0 weight percent to about 0.5 weight percentaluminum, from about 0 weight percent to about 2 weight percent nickel,from about 0 weight percent to about 0.5 weight percent tantalum, fromabout 0 weight percent to about 0.1 weight percent carbon, and fromabout 0 weight percent to about 0.1 weight percent nitrogen, with thebalance being iron and incidental impurities; wherein the NFA comprisesa number density of at least about 10²² m⁻³ nanofeatures comprisingtitanium, oxygen and at least one element derived from the oxide addedduring preparation of the NFA or from the alloy matrix.

Typically, as noted previously, directly processing the as-consolidatedNFAs at high temperatures (˜1900° F. or above) may degrade themechanical properties of the alloy. This may be due, in part, to theincrease in the grain size of the NFA with the increase in temperatureabove about 1800 degrees Fahrenheit. Usually, an “as-prepared” or“as-consolidated” NFA workpiece has a fine microstructure having anaverage grain size less than about 2 microns. In certain instances, theaverage grain size is between about 1 micron and 2 microns. In this finemicrostructure, a percentage of coarse grains (grains larger than about1 micron) may be low, for example less than about 5 percent based on thetotal grains in the microstructure.

FIG. 1A and FIG. 1B show the effect of a high temperature on themicrostructure of a NFA workpiece. FIG. 1A is a scanning electronmicroscope (SEM) micrograph of an “as-consolidated” workpiece (i.e.without a heat treatment); and FIG. 1B is a SEM micrograph of theworkpiece after heating it at 2000 degrees Fahrenheit for 24 hours. FIG.1B clearly shows a grain growth (i.e., an increase in percentage ofcoarse that is large grains) in the NFA workpiece with the increase intemperature. It was observed that the percentage of coarse grains (thathave grain size greater than about 1 micron, and in some certaininstances, greater than about 5 microns) in the NFA workpiece afterheating it up to 2000 degrees Fahrenheit is significantly larger (˜4times) than the percentage of coarse grains in the alloy of theworkpiece at about 1800 degrees Fahrenheit. After heating the workpieceat 2000 degrees Fahrenheit, for about 24 hours, the average grain sizeof the NFA workpiece is up to about 50 microns. This grain growth withthe rise of temperature limits the processing of the NFA at hightemperatures, i.e. at temperatures higher than about 1900 degreesFahrenheit. Moreover, processing NFAs with coarsening grains by using ahigh strain rate technique (for example, forging) may lead to cracking,and thus damaging the resulting article.

It has been surprisingly discovered by the inventors that the presentmethod enables the processing of the NFAs at high temperatures (morethan about 1900° F.) and/or at high strain rates without a significantdegradation in the mechanical properties of a resulting article at anoperating temperature. An operating temperature, at which these articlesare used, is generally lower than a processing temperature, at which theNFAs are processed. The ability to process the NFAs at high temperaturesand/or high strain rates advantageously enables the use of theconventional high strain rate processing techniques for manufacturing adesired article from the NFA and thus maintaining low manufacturingcosts.

According to some embodiments of the invention, the present methodincludes steps of introducing a quantity of strain into a workpiece thatincludes a nanostructured ferritic alloy (NFA) at a first temperaturebelow about 1900 degrees Fahrenheit to form a strained workpiece,heating the strained workpiece to a second temperature and deforming thestrained workpiece at the second temperature. The second temperature isat least about 1900 degrees Fahrenheit. In these embodiments, thequantity of strain is first introduced into the NFA workpiece at atemperature below about 1900 degrees Fahrenheit before heating and/orprocessing (i.e., hot-working) the workpiece at a higher temperature.The quantity of strain introduced into the workpiece at the firsttemperature is effective to substantially inhibit grain growth in thestrained workpiece during the subsequent heating and the deforming atthe second temperature. This introduction of strain into the workpieceat the first temperature enables the deforming and/or the heating of theworkpiece at a subsequent higher temperature, and thus the workpiece canbe processed or hot-worked at high temperatures while preserving themicrostructure to procure the desired mechanical properties.

The workpiece may be fabricated by consolidating a powder of ananostructured ferritic alloy (NFA) (as discussed previously) by anytechnique as known in the art. In one embodiment, the workpiece isfabricated by hot isostatic pressing (HIP). Other compaction techniquesinclude hot compaction, extrusion, or roll compaction.

As noted, a quantity of strain is first introduced into the NFAworkpiece at a first temperature below about 1900 degrees Fahrenheit. Inother words, the workpiece is deformed at the first temperature. Withoutbeing bound by any theory, it is believed that by deforming theworkpiece at the first temperature, a retained plastic strain interactswith the stable nanofeatures and effectively pins grain boundaries. Thispinning of the grain boundaries does not allow the grains of the finemicrostructure of the workpiece to substantially grow in size, and thussubstantially inhibits grain growth of the microstructure of thestrained workpiece during the heating, the processing, or both at asecond temperature. Advantageously, the microstructure of the strainedworkpiece does not substantially change on heating or with a rise intemperature, and is maintained or stabilized for any further heating orprocessing, for example high strain rate processing at a hightemperature.

It is desirable to have no or little (<1 percent) growth in the grainsize of the strained workpiece during the subsequent heating and/or theprocessing at a temperature of at least about 1900 degrees Fahrenheit.However, there may be a substantial growth in the grain size of thestrained workpiece. As used herein, a substantial growth may refer to anincrease of up to about 10 percent in the percentage of coarse grains inthe microstructure. In some embodiments, the increase in the percentageof coarse grains in the microstructure is in a range from about 1percent to about 5 percent during the heating or the processing at thesecond temperature. FIG. 2A and FIG. 2B show SEM micrographs of aworkpiece, respectively, after extruding the workpiece at 1700 degreesFahrenheit and after heating the extruded workpiece at 2000 degreesFahrenheit for about 24 hours. No significant change in the grain sizeof the workpiece was observed with the heat treatment at the hightemperature after the extrusion at 1700 degrees Fahrenheit.

The stability of the microstructure of the strained workpiece may dependspecifically on the first temperature in conjunction with the quantityof strain introduced into the workpiece. As alluded to previously, thequantity of strain introduced into the workpiece at the firsttemperature is effective to substantially inhibit grain growth in thestrained workpiece during the heating and the deforming at the secondtemperature. The effectiveness of the strain introduced into theworkpiece may be a result of an amount of a strain applied to theworkpiece and a strain rate at which the strain is applied to theworkpiece. That is, the workpiece may be deformed at the firsttemperature by applying a specific strain with a specific strain rate.The workpiece may be deformed by any technique including forging,compaction, extrusion, and rolling. In certain embodiments, theworkpiece is deformed by extrusion at the first temperature.

In some embodiments, at least about 40 percent strain with a strain rateof less than about 1 inch/inch/sec is applied on the workpiece. In someembodiments, a strain ranging from about 40 percent to about 70 percentis desirable for effectively inhibiting the grain growth. In someembodiments, the strain is applied at a strain rate ranging from about0.005 inch/inch/sec to about 0.9 inch/inch/sec. The first temperature isgenerally below 1900 degrees Fahrenheit. In some embodiments, the firsttemperature ranges from about 1600 degrees Fahrenheit to about 1900degrees Fahrenheit, and in some certain embodiments, from about 1700degrees Fahrenheit to about 1800 degrees Fahrenheit.

Advantageously, the strained workpiece having the stabilizedmicrostructure can be processed at a high temperature (i.e., a highprocessing temperature) and/or at a high strain rate for forming anarticle. A high temperature refers to a temperature equal to or higherthan 1900 degrees Fahrenheit. A high strain rate refers to a strain ratehigher than about 1 inch/inch/sec. In some embodiments, the strain rateis higher than about 5 inch/inch/sec, and in particular embodiments,higher than about 10 inch/inch/sec. In some embodiments, afterintroducing a quantity of strain into the workpiece, the strainedworkpiece may be first heated to the second temperature and thendeformed at the second temperature.

In some embodiments, the strained workpiece is deformed at a secondtemperature that is at least about 1900 degrees Fahrenheit. In someembodiments, the second temperature ranges from about 1950 degreesFahrenheit to about 2300 degrees Fahrenheit, and in certain embodiments,from about 2000 degrees Fahrenheit to about 2200 degrees Fahrenheit.

The step of deforming at the second temperature may be performed to forman article from the strained workpiece. The deforming step may includedeforming the strained workpiece with a high strain rate technique, forexample high strain rate forging. In some embodiments, the strainedworkpiece is deformed with a strain rate in a range from about 10inch/inch/sec to about 30 inch/inch/sec. Other suitable techniques mayinclude extrusion, compaction, or rolling. In some embodiments, aworkpiece is first extruded at the first temperature and then processedby forging at the second temperature. In some embodiments, aturbomachinery component, such as a bolt, may be manufactured by thedisclosed method.

In some embodiments, it is desirable to deform, for example, by forgingthe strained workpiece at a temperature higher than 1900 degreesFahrenheit. Processing a strained workpiece with a high strain rate at alow temperature, for example below 1900 degrees Fahrenheit may lead tocracking of the resulting NFA article/component. FIG. 3 shows flowstress curves for the NFA workpiece samples that were compressed at 1900degrees Fahrenheit and 2100 degrees Fahrenheit. Each of these sampleswas first extruded at 1700 degrees Fahrenheit and then subsequentlycompressed at a strain rate of 20 inch/inch/sec. It was observed that asample that was first extruded at 1700 degrees Fahrenheit andsubsequently compressed at 1700 degrees Fahrenheit, was cracked. Thisdemonstrated that this temperature, about 1700 degrees Fahrenheit, wastoo low to conduct a high strain rate processing. It was furtherobserved that the samples that were compressed at 1900 degreesFahrenheit and 2100 degrees Fahrenheit produced no cracks. Furthermore,as clearly seen from FIG. 3, the flow stresses for the samples areconducive to the component manufacturing.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1. A method comprising: introducing a quantity of strain into aworkpiece at a first temperature below about 1900 degrees Fahrenheit toform a strained workpiece; heating the strained workpiece to a secondtemperature, wherein the second temperature is at least about 1900degrees Fahrenheit; and deforming the strained workpiece at the secondtemperature, wherein the workpiece comprises a nanostructured ferritcalloy (NFA), and wherein the quantity of strain introduced into theworkpiece at the first temperature is effective to substantially inhibitgrain growth in the strained workpiece during the heating and thedeforming at the second temperature.
 2. The method of claim 1, whereinthe workpiece comprises a grain size distribution having an averagegrain size less than about 2 microns.
 3. The method of claim 1, whereinintroducing a quantity of strain into the workpiece at the firsttemperature comprises applying at least about 40 percent strain.
 4. Themethod of claim 1, wherein introducing a quantity of strain into theworkpiece at the first temperature comprises deforming the workpiece ata strain rate lower than about 1 inch/inch/sec.
 5. The method of claim1, wherein the first temperature ranges from about 1600 degreesFahrenheit to 1900 degrees Fahrenheit.
 6. The method of claim 1, whereinthe second temperature ranges from about 1950 degrees Fahrenheit toabout 2300 degrees Fahrenheit.
 7. The method of claim 1, whereindeforming the strained workpiece comprises deforming the strainedworkpiece at a strain rate of at least about 1 inch/inch/sec.
 8. Themethod of claim 1, wherein deforming the strained workpiece comprisesdeforming the strained workpiece at a strain rate ranging from about 1inch/inch/sec to about 30 inch/inch/sec.
 9. The method of claim 1,wherein the deforming step is performed by compaction, forging,extusion, or rolling.
 10. An article formed by the method according toclaim
 1. 11. The article of claim 10, wherein the article is aturbomachinery component.
 12. A method of forming a turbomachinerycomponent, comprising the steps of: introducing a quantity of straininto a workpiece at a first temperature below 1900 degrees Fahrenheit toform a strained workpiece, wherein the workpiece comprises a nanostructured ferritc alloy (NFA); heating the strained workpiece to asecond temperature, wherein the second temperature is at least about1900 degrees Fahrenheit; and forging the strained workpiece at thesecond temperature at a strain rate of at least about 1 inch/inch/sec,wherein the quantity of strain introduced into the workpiece at thefirst temperature is effective to substantially inhibit grain growth inthe strained workpiece during the heating and the forging at the secondtemperature.